Field of the Invention
The invention relates to a method and system for alignment of a wellbore completion inside a casing of a well. More specifically the invention relates to a system and method for a one-way continuous inward movement of the well completion without the need of any reversing action or the need for mechanical locating elements in the casing and locating mating elements on the completion string.
Description of the Related Art
In the placement of tools and equipment (e.g., perforating tools, packers, valves, sensors, inductive coils, etc.) in a wellbore, the accuracy of depth referenced from the surface is known to entail a certain degree of uncertainty. While the length of casing joints installed in the well are generally known at the surface, the influences of the wellbore environment (e.g., compression, tension, and temperature) affect the length of the casing joints in the wellbore. Due to this uncertainty, it is of advantage to provide position references in the wellbore which may be used to determine the (relative) position of an element being run into the well. Currently, the placement of equipment in proximity to elements in a wellbore may be accomplished by use of mechanical locating members in the wellbore casing which engage locating mating members on the tool (or string) being run into the well.
Each of these methods generally requires a “dummy run,” wherein the tool (e.g., string) is run into the well until the element in the wellbore is detected. The string is then retracted and the length adjusted such that the desired length is reinserted into the wellbore, for example, to land the tubing hanger with the down-hole elements in close proximity. This approach has a significant disadvantage when the well is a subsea well wherein the wellhead is located on the seafloor. In such cases, the completion may be run in on a workstring to determine the location of the downhole element. Then the workstring may be removed, the completion length adjusted, and the completion and workstring run in again and, finally, the workstring may be retrieved yet again, requiring substantial time and associated costs, and increasing the opportunity for injury to personnel and property. For wellheads located on the sea floor, and for deep sea waters, the wellhead may be up to three kilometers below the vessel or platform. In such installations there is a common problem that the exact length of the necessary tubing is not well known, and alignment of tubing and casing in the bottom of the well becomes difficult.
Another approach is to run a wireline tool to determine the depth of the wellbore element prior to running the completion. This requires the presence of additional equipment and personnel on the rig, and requires time and associated costs to rig up, run in, pull out, and rig down.
Yet another approach is to utilize a locating element on the casing with a mating element on the completion string such that the locating element and the mating element engage when the completion string reaches the desired depth.